Robust pet-tracker with sensitive insides

Ultrasonic welding is the suitable technology for joining a water and dust-tight casing for the innovative detector. This way, the hardware, including a sensitive antenna, is well protected - even off-road in the mud or bathing in the sea.

The Düsseldorf start-up Prothelis was searching for a suitable joining process for its innovative product Greta and weighed up various mechanical and thermal methods against each other. The requirements for the process were:

• Fast
• Safe, to protect the internal electronics
• Strong and tight according to IP 67

The GRETA casing is made of ABS (acrylonitrile butadiene styrene). Due to the number of pieces, the desired cycle times and the material, it was decided to use ultrasonic welding and the company found the right supplier for the joining technology in Herrmann Ultraschall.

Is that possible?

So that meaningful, close-to-production results can be swiftly obtained for the ultrasonic welding of new components, Herrmann Ultraschall offers trial welds in every desired material or material combination and with all common joint designs. Near-field or far-field welds are possible, depending on how far away the sonotrode coupling surface will be from the joint line on the later plastic component. During the tests, a high-speed camera is used to record the melting process and potential notch effects; the tensile strength of the joint is determined and torsional loads acting on the part are also tested.

Unusual test subject

The initial tests for the Prothelis project were carried out on an unusual test weld specimen – a toy elephant had to be the stand-in. Real shell samples were not yet available and Herrmann’s standard test weld specimen was too small.

Prothelis was there at the tests in the laboratory at Herrmann Ultraschall, and measured the sensitive electronics before and afterwards. Would 20 kHz, i.e. 20,000 movements a second, have an effect? The measurements after the welds confirmed perfect functioning of the electronics. Further trials with genuine samples showed that the tracker keeps tight at 2 bar, which is 20 meters underwater. Prothelis therefore approved ultrasonic welding as the joining technology.